Noise-reducing mower blade

ABSTRACT

A mower blade includes a body including an axis of rotation about which the blade is configured to rotate, a first body portion extending in a first direction from the axis of rotation, and a second body portion extending in a second opposite direction from the axis of rotation, wherein the second body portion is asymmetrically shaped with respect to the first body portion such that the center of mass of the blade lies on the axis of rotation.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/622,995, filed Apr. 11, 2012, which is incorporated herein byreference in its entirety. This application also claims the benefit ofU.S. Provisional Application No. 61/708,528, filed Oct. 1, 2012, whichis incorporated herein by reference in its entirety.

BACKGROUND

The present application relates to cutting systems used on lawn andgarden equipment. Typically, lawn and garden equipment such aswalk-behind lawn mowers, tractors, riding mowers, zero-turn radiusmowers etc. cut grass or other vegetation with a cutter bar or barblade. An example of a typical blade is shown in U.S. Pat. No.5,711,141, which is herein incorporated by reference in its entirety.Such a blade is a substantially flat rectangular bar having a centerpoint about which the blade rotates. Two or more sharpened edges areprovided on opposing sides of the center point. The blade is spun aboutthe center point to cut grass or vegetation. Typically the blade isattached (either directly or indirectly) to an internal combustionengine, electric motor or other prime mover. The blade is spun at aspeed high enough to cut grass. Typical blade speeds can range from 2000to 4000 rotations per minute (RPM). Typical cutting blades are alsoprovided with structures to direct airflow in a desired direction. Forexample, a mulching blade may include two wings or similar shapes todirect air and grass in an upward direction to establish a vacuum belowthe blade, thereby causing the grass to stand up while being cut.

A shortcoming of typical bar blades is noise. The cutting blade, whenspun at cutting speeds, is similar to a fan and can generate much of thenoise associated with a lawn mower. A consumer may desire a mower withreduced noise or sound levels.

SUMMARY

One embodiment of the invention relates to a mower blade including abody including an axis of rotation about which the blade is configuredto rotate, a first body portion extending in a first direction from theaxis of rotation, and a second body portion extending in a secondopposite direction from the axis of rotation, wherein the second bodyportion is asymmetrically shaped with respect to the first body portionsuch that the center of mass of the blade lies on the axis of rotation.

Another embodiment relates to a mower blade including two symmetricalbody portions disposed on either side of an axis of rotation, whereineach body portion includes a leading edge having a first sharpened edgeformed along at least a portion of the leading edge, and a trailing edgehaving a second sharpened edge formed along at least a portion of thetrailing edge.

Another embodiment relates to a mower blade including a mountingstructure defining an axis of rotation about which the lawn mower bladeis configured to rotate, a cutting portion extending in a firstdirection from the axis of rotation, wherein the cutting portionincludes a lift feature and a leading edge having a first sharpened edgeformed along at least a portion of the leading edge, and a counterweightportion extending in a second direction from the axis of rotation, thecounterweight portion including a counterweight so that the center ofmass of the mower blade lies on the axis of rotation.

Alternative exemplary embodiments relate to other features andcombinations of features as may be generally recited in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will become more fully understood from the followingdetailed description, taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a perspective view of a lawn mower according to an exemplaryembodiment.

FIG. 2 is a bottom view of the lawn mower of FIG. 1.

FIG. 3 is a perspective view of a lawn mower blade according to anexemplary embodiment.

FIG. 4 is a top view of the lawn mower blade of FIG. 3.

FIG. 5 is a front view of the lawn mower blade of FIG. 3.

FIG. 6 is a sectional view along line 6-6 of the lawn mower blade ofFIG. 4.

FIG. 7 is a perspective view of a lawn mower blade according to anexemplary embodiment.

FIG. 8 is a top view of the lawn mower blade of FIG. 7.

FIG. 9 is a side view of the lawn mower blade of FIG. 7.

FIG. 10 is a front view of the lawn mower blade of FIG. 7.

FIG. 11 is a sectional view along line 11-11 of the lawn mower blade ofFIG. 10.

FIG. 12 is a sectional view along line 12-12 of the lawn mower blade ofFIG. 10.

FIG. 13 is a perspective view of a lawn mower blade according to anexemplary embodiment.

FIG. 14 is a top view of the lawn mower blade of FIG. 13.

FIG. 15 is a side view of the lawn mower blade of FIG. 13.

FIG. 16 is a front view of the lawn mower blade of FIG. 13.

FIG. 17 is a perspective view of a lawn mower blade according to anexemplary embodiment.

FIG. 18 is a top view of the lawn mower blade of FIG. 17.

FIG. 19 is a side view of the lawn mower blade of FIG. 17.

FIG. 20 is a front view of the lawn mower blade of FIG. 17.

FIG. 21 is a perspective view of a lawn mower blade according to anexemplary embodiment.

FIG. 22 is a top view of the lawn mower blade of FIG. 21.

FIG. 23 is a side view of the lawn mower blade of FIG. 21.

FIG. 24 is a front view of the lawn mower blade of FIG. 21.

FIG. 25 is a perspective view of a lawn mower blade according to anexemplary embodiment.

FIG. 26 is a top view of the lawn mower blade of FIG. 25.

FIG. 27 is a side view of the lawn mower blade of FIG. 25.

FIG. 28 is a front view of the lawn mower blade of FIG. 5.

DETAILED DESCRIPTION

Before turning to the figures, which illustrate the exemplaryembodiments in detail, it should be understood that the application isnot limited to the details or methodology set forth in the descriptionor illustrated in the figures. It should also be understood that theterminology is for the purpose of description only and should not beregarded as limiting.

Referring to FIGS. 1-2, a walk-behind lawn mower 50 according to anexemplary embodiment is illustrated. Lawn mower 50 includes a primemover 52 (e.g., an internal combustion engine, an electric motor, etc.)that rotates a blade 110. Blade 110 is positioned within a cuttingchamber 54 defined at least in part by a mower deck 56 that includes anupper surface 58 and a sidewall 60. Cutting chamber 54 is the spacebetween the ground and the mower deck 56 in which blade 110 rotatesduring normal use.

Referring to FIGS. 3-6, blade 110 for lawn, grass or vegetation cuttingis illustrated according to an exemplary embodiment. Blade 110 may beused on a walk-behind lawn mower as shown in FIGS. 1-2, a tractor, ariding mower, a zero-turn radius mower, or other suitable outdoor powerequipment. Blade 110 includes a bar 112 and a counterweight 114. Asillustrated in FIGS. 3-6, counterweight 114 is integrally formed withbar 112 as a single piece mower blade 110. For example, blade 110 can bestamped or cast as a single piece. In other embodiments, blade 110 isformed by multiple pieces fastened together (e.g., welded, bolted,riveted, assembled with fasteners, etc.). As shown in FIGS. 3 and 4,blade 110 has a longitudinal axis 111 that is substantiallyperpendicular to an axis of rotation 113 that extends through theblade's center of rotation and mounting hole 118. A transverse axis 115is substantially perpendicular to both longitudinal axis 111 and axis ofrotation 113.

Bar 112 is generally an elongated body and includes a leading edge 116,a trailing edge 135, mounting holes 118 and 122, a lift feature 120, andan end portion 124 opposite counterweight 114. As shown in FIG. 5, bar112 also includes a cutting portion 117, a lift portion 119, and atransition portion 121.

Leading edge 116 is considered the “leading” edge of blade 110 becauseit leads with respect to the intended rotation of blade 110. Withreference to FIG. 4, blade 110 is intended for clockwise rotation.Trailing edge 135 “trails” with respect to the intended rotation ofblade 110 and is located opposite longitudinal axis 111 from leadingedge 116 of blade 110. Sharpened or cutting portion or edge 139 extendsalong leading edge 116 from lift feature 120 of lift portion 119, alongtransition portion 121, and along cutting portion 117 to the midpoint ofrounded end portion 124. Sharpened edge 139 is sharpened for cuttinggrass. In some embodiments, sharpened edge 139 extends for differentlengths along leading edge 116 and end portion 124 of blade 110. Forexample, sharpened edge 139 can extend across a portion or the entiretyof transition portion 121 and/or across a portion of lift portion 119.As blade 110 rotates, sharpened edge 139 contacts grass or vegetation toprovide the cutting action of the lawn mower. In some embodiments, oneor more additional sharpened edges at other locations along blade 110may be incorporated (e.g., to improve cutting performance).

Mounting hole 118 is located at axis of rotation 113. Mounting hole 118is the primary mounting point to attach blade 110 to a mower, whilemounting holes 122 provide supplemental mounting points for attachingblade 110 to the mower. Blade 110 may be mounted directly to an engineoutput shaft if, for example, blade 110 is installed on a small walkbehind mower. Alternatively, blade 110 could be mounted to spindles thatallow for rotation of blade 110, if for example, blade 110 is installedon a larger, multi-blade walk behind mower, tractor, riding mower, etc.Blade 110 is secured to that blade 110 is generally horizontal to axisof rotation 113. In some embodiments, mounting structures other than oneor more mounting holes may be used for mounting blade 110 to a mower(e.g., a mounting boss, a mounting flange, a mounting stud, etc.).

FIG. 2 illustrates blade 110 positioned within cutting chamber 54 ofmower deck 56. Lift feature 120 generates lift or a vacuum below blade110 within the cutting chamber 54 as blade 110 rotates. The lift causesthe grass within the cutting chamber to stand or raise up in a generallyvertical direction, allowing for a better, more complete cut of thegrass. It is believed that placement of lift feature 120 closer to thecenter of rotation of blade (i.e., axis of rotation 113) is advantageouswith respect to sound generated by the motion of blade 110 in that liftfeature 120 is traveling at a slower linear speed than the tip of blade110 near cutting edge 116, thus generating less noise. Typical bladeswill provide one or more lifting airfoils at the outer or end portionsof the blade, whereas blade 10 includes a single lift feature 120provided closer to the center of rotation. In some embodiments, liftfeature 120 extends from about 2.5 inches to 5.5 inches from the centeror rotation of blade 110. In other embodiments, the size and placementof lift feature 120 varies. As shown in FIGS. 2-6, lift feature 120comprises an airfoil. As shown in FIG. 6, airfoil is angled upward fromthe planar portion of lift portion 119. As shown in FIG. 6, airfoilangles upwards from an interior portion of blade 110. In otherembodiments, airfoil angles upwards from leading edge 137. In otherembodiments, other structures capable of producing lift due to rotationof blade 110 may be used in place of an airfoil (e.g., twisted regionshown in FIGS. 7-11).

End portion 124 is rounded. Rounded end portion 124 acts to reduce thesurface area at the end of bar 112 relative to a square end (i.e., notrounded), which is believed to reduce noise produced by blade 110 duringrotation relative to a bar with a square end.

Cutting portion 117 is substantially planar. Lift portion 119 issubstantially planar except for the lift feature 120. Transition portion121 connects lift portion 119 to cutting portion 117 so that cuttingportion 117 is offset (e.g., positioned lower along axis of rotation 113when blade 110 is in its normal operating orientation, as shown in FIG.3) from lift portion 119, with the planar regions of cutting portion 117and lift portion 119 being generally parallel to one another.

The shape of counterweight 114 may be any suitable shape sufficient tobalance blade 110 about axis of rotation 113. As shown in FIG. 2,counterweight 114 extends transversely outward from longitudinal axis111 to a greater width than bar 112. Counterweight 114 includes twowings or extensions 123 and 125 that form the portions of counterweight114 that are wider than bar 112. Extension 125 is located on theopposite side of blade 110 from leading edge 116 (with longitudinal axis111 between the two). Second sharpened edge 127 extends along theleading edge of extension 125 and onto a portion of bar 112 (e.g. afillet connecting extension 125 to bar 112). Similarly to sharpened edge139, sharpened edge 127 contacts grass or vegetation as blade 110rotates to provide the cutting action for a lawn mower. Second sharpenededge 127 helps to prevent the accumulation of grass clippings oncounterweight 114. In some embodiments, counterweight 114 does notinclude second sharpened edge 127 or second sharpened edge extends alonga portion of leading edge of counterweight 114.

A sacrificial or grinding portion 129 of counterweight 114 is located atthe end of blade 110 opposite end portion 124. During use of blade 110,sharpened edges 116 and 127 will eventually dull. After sharpened edges116 and 127 are re-sharpened, which removes material from sharpenedregions 116 and 127, material may need to be removed from counterweight114 to properly balance blade 110. Grinding portion 129 provides aconvenient location from which material can be removed fromcounterweight 114 as needed to balance blade 110. Preferably, blade 110is balanced in the x-direction (along longitudinal axis 111) and in they-direction (along transverse axis 115). In the embodiment shown inFIGS. 1-4, blade 110 is not balanced in the z-direction (along axis ofrotation 113) due to the change in elevation between lift region 119 andcutting region 117.

Blade 110 may be considered to have two sides or portions, one on eitherside of mounting hole 118 and axis of rotation 113. On the first orcutting portion of axis of rotation 113, bar 112 extends away from axisof rotation 113 and includes leading edge 116, lift feature 120, and endportion 124. On the opposing or counterweight portion of axis ofrotation 113, bar 112 extends to counterweight 114. The counterweightportion of blade 110 is sized and weighted to balance (e.g., statically,dynamically, or both) the cutting portion of blade 110. Thecounterweight portion is not symmetrical with the cutting portion ofblade 110 (i.e., counterweight portion is shaped differently than thecutting portion). Counterweight 114 is arranged so that the center ofmass of blade 110 lies on axis of rotation 113, such that blade 110 isbalanced about axis of rotation 113 in at least the x-direction (alonglongitudinal axis 111) and in the y-direction (along transverse axis115). The mid-point of the length (i.e., one half of the length of blade110 from the end of the counterweight portion to the end of the cuttingportion) is located in the cutting portion of blade 110 because of thedifferent lengths of the two portions of blade 110 (i.e., thecounterweight portion is shorter than the cutting portion).

An outer portion 131 of blade 110 includes leading edge 116, trailingedge 135, and end portion 124. As shown in FIG. 2, both leading edge 116and trailing edge 135 taper towards longitudinal axis 111 as they extendaway from axis of rotation 113 towards the end of bar 112. Leading edge116 and trailing edge 135 terminate in rounded end portion 124. Leadingedge 116 and trailing edge 135 can be considered to be arcuate, curved,or bending. In other embodiments, trailing edge 135 is straight. Indifferent embodiments, sharpened edge 139 may extend along at least aportion of leading edge 116, along the entirety of leading edge 116,along at least a portion of end portion 124, and/or along the entiretyof end portion 124.

FIGS. 6-11 illustrate a mower blade 210 according to another exemplaryembodiment. Blade 210 is similar to blade 110 described above.Accordingly, components of blade 210 referred to by numerals in the 200sare similar to components of blade 110 referred to by similar numeralsin the 100s. Differences between blade 210 and blade 110 are describedin more detail below.

Trailing edge 235 includes a sharpened edge 241. In differentembodiments, sharpened edge 241 may extend along at least a portion oftrailing edge 235, along the entirety of trailing edge 235, along atleast a portion of end portion 224, and/or along the entirety of endportion 224. Sharpened edge 241 forms a bevel that can be angled eitherupwards or downwards relative to the axis of rotation 213 with respectto the normal operating orientation of blade 210. Sharpening or bevelingat least a portion of trailing edge 235 to form sharpened edge 241 helpsto reduce the noise produced by blade 210 in operation. It is believethat sharpened edge 241 improves the slipstream created by blade 210 byreducing its turbulence and thereby reducing noise. In some embodiments,trailing edge of counterweight 214 also includes a sharpened or bevelededge.

Lift feature 220 is a twisted region or twisted portion of bar 210.Twisted portion includes an inboard section 255 and an outboard section257. Each section 255 and 257 is twisted about longitudinal axis 211, oran axis substantially parallel to longitudinal axis, so that sections255 and 257 are not coplanar with a base portion 251 that issubstantially planar and includes mounting holes 218 and 222. Inboardsection 255 is twisted in the opposite direction than outward section257 (e.g. inboard section 255 is twisted clockwise, when viewed alonglongitudinal axis 211 from a point further outboard than outboardsection 257 and outboard section 257 is twisted counterclockwise whenviewed from the same point). As illustrated, the magnitude of the twistrelative to horizontal (e.g. with reference to base portion 251) variesfor each of sections 255 and 257. In other embodiments, the amount oftwist for each section 255 and 257 relative to horizontal may be thesame. In some embodiments, the vertical distance (i.e., as measured withrespect to axis of rotation 213) from the uppermost point to thelowermost point of inboard section 255 is 0.403 inches. In someembodiments, the vertical distance (i.e., as measured with respect toaxis of rotation 213) from the uppermost point to the lowermost point ofoutboard section 257 is 0.311 inches. In other embodiments, thisvertical distance is 0.570 inches.

Cutting portion 217 is outboard from lift portion 219 relative to axisof rotation 213. In the cutting portion 217, leading edge 216 is lowerthan leading edge 216 in the planar regions of the lift portion 219 withrespect to axis of rotation 213 when blade 210 is in its normaloperating orientation.

FIGS. 12-15 illustrate a mower blade 310 according to another exemplaryembodiment. Blade 210 is similar to blades 210 and 110 described above.Accordingly, components of blade 310 referred to by numerals in the 300sare similar to components of blades 210 and 110 referred to by similarnumerals in the 200s and 100s, respectively.

Leading edge 316 is straight and terminates at rounded end portion 324.Similarly, sharpened edge 339 is straight except for a rounded portionalong rounded end portion 324.

FIGS. 16-19 illustrate a mower blade 410 according to another exemplaryembodiment. Blade 410 is similar to blades 310, 210, and 110 describedabove. Accordingly, components of blade 410 referred to by numerals inthe 400s are similar to components of blades 310, 210, and 110 referredto by similar numerals in the 300s, 200s, and 100s, respectively.

Leading edge 416 and sharpened edge 439 are straight. Similarly,trailing edge 435 and sharpened edge 441 are straight End portion 424terminates in a substantially flat tip 459 (i.e., substantially parallelto transverse axis 415. A notch 461 is formed in tip 459 at the end oftip 459 adjacent trailing edge 437. A notch 463 and a notch 465 areformed in trailing edge 437 near tip 459. Notch 463 extends furthertowards longitudinal axis 411 than notch 465. Notches 461, 463, and 465help reduce the noise produced by blade 410 when in operation.

FIGS. 20-23 illustrate a mower blade 510 according to another exemplaryembodiment. Blade 510 is similar to blades 410, 310, 210, and 110described above. Accordingly, components of blade 510 referred to bynumerals in the 500s are similar to components of blades 410, 310, 210,and 110 referred to by similar numerals in the 400s, 300s, 200s, and100s, respectively.

Blade 510 is substantially symmetrical about axis of rotation 513 anddoes not include a counterweight similar to those of blades 110, 210,310, and 410 (e.g., counterweight 214 of blade 210). Blade 510 includestwo symmetrical outer portions 531, outer portion 531A and outer portion531B. Each outer portion 531 includes a leading edge 533, a trailingedge 535, and an end portion 524. Leading edge 533 includes sharpenededge 539 and trailing edge 535 includes sharpened edge 241. Both leadingedge 533 and trailing edge 535 are rounded and terminate in rounded endportion 524.

FIGS. 24-27 illustrate a mower blade 610 according to another exemplaryembodiment. Blade 610 is similar to blades 510, 410, 310, 210, and 110described above. Accordingly, components of blade 610 referred to bynumerals in the 600s are similar to components of blades 510, 410, 310,210, and 110 referred to by similar numerals in the 500s, 400s, 300s,200s, and 100s, respectively.

Blade 610 is substantially symmetrical about axis of rotation 613 anddoes not include a counterweight similar to those of blades 110, 210,310, and 410 (e.g., counterweight 314 of blade 310). Blade 610 includestwo outer portions 631, outer portion 631A and outer portion 631B. Eachouter portion 631 includes leading edge 616, a trailing edge 635, and anend portion 624. Leading edge 516 is straight and terminates at roundedend portion 624. Similarly, sharpened edge 539 is straight except for arounded portion along rounded end portion 524. Trailing edge 635 isrounded and terminates at rounded end portion 624.

Mower blades can be evaluated in terms of noise production and cuttingeffectiveness. Improving one may negatively impact the other. Therefore,blade design typically requires tradeoffs between noise production andcutting effectiveness. Blades designed for different uses (e.g.,mulching, side discharge, bagging) also require different relativestrengths with respect to noise production and cutting effectiveness.For example, cutting performance is of primary concern for a mulchingmower blade.

A primary factor in cutting performance is the lift produced by theblade. The more lift produced in the cutting chamber, the more likelygrass is stand or raise to a vertical position, which improves cuttingperformance. Lift also helps with cut-grass discharge for side dischargeand bagging applications.

Noise production is believed to be affected by several factorsincluding: blade width, blade thickness, amount of lift, blade endtreatment, the trailing edge, and the clearance between the end of theblade and the sidewall of the mower deck. Reducing the blade width andthe blade thickness may reduce noise production. Reducing lift mayreduce noise production. A rounded blade end treatment (e.g., blades110, 210, 310, 510, and 610) or a blade end treatment including slots(e.g., blade 410) may reduce noise production. A sharpened edge on thetrailing edge of the blade (e.g., blades 210, 310, 410, 510, and 610)may reduce noise production. Increasing the gap between the end of theblade and the sidewall of the mower deck may reduce noise production.

Varying the noise production factors and the lift produced by the bladeallows different embodiments of blades 110, 210, 310, 410, 510, and 610to emphasize either reducing noise production or improving cuttingeffectives or be optimized for different uses (e.g., mulching, sidedischarge, bagging) while producing noise levels lower than a typicalmower blade.

The construction and arrangement of the apparatus, systems and methodsas shown in the various exemplary embodiments are illustrative only.Although only a few embodiments have been described in detail in thisdisclosure, many modifications are possible (e.g., variations in sizes,dimensions, structures, shapes and proportions of the various elements,values of parameters, mounting arrangements, use of materials, colors,orientations, etc.). For example, some elements shown as integrallyformed may be constructed from multiple parts or elements, the positionof elements may be reversed or otherwise varied and the nature or numberof discrete elements or positions may be altered or varied. Accordingly,all such modifications are intended to be included within the scope ofthe present disclosure. The order or sequence of any process or methodsteps may be varied or re-sequenced according to alternativeembodiments. Other substitutions, modifications, changes, and omissionsmay be made in the design, operating conditions and arrangement of theexemplary embodiments without departing from the scope of the presentdisclosure.

What is claimed is:
 1. A mower blade, comprising: a body including anaxis of rotation about which the blade is configured to rotate; a firstbody portion extending in a first direction from the axis of rotation;and a second body portion extending in a second opposite direction fromthe axis of rotation, wherein the second body portion is asymmetricallyshaped with respect to the first body portion such that the center ofmass of the blade lies on the axis of rotation.
 2. The mower blade ofclaim 1, wherein a mid-point of the length of the mower blade is locatedin the first body portion.
 3. The mower blade of claim 1, wherein thefirst body portion includes a sharpened edge.
 4. The mower blade ofclaim 3, wherein the first body portion comprises a leading edge and atrailing edge located opposite the leading edge, and wherein thesharpened edge is formed along at least a portion of the leading edge.5. The mower blade of claim 4, wherein the first body portion furtherincludes a rounded end.
 6. The mower blade of claim 5, wherein thetrailing edge tapers to the rounded end.
 7. The mower blade of claim 6,further comprising: a second sharpened edge formed along at least aportion of the trailing edge.
 8. The mower blade of claim 7, wherein theleading edge is straight.
 9. The mower blade of claim 4, wherein thefirst body portion further includes a lift feature.
 10. The mower bladeof claim 4, wherein the lift feature is an air foil.
 11. The mower bladeof claim 4, wherein the lift feature is a twisted region.
 12. The mowerblade of claim 3, further comprising: a slot extending from the trailingedge towards the leading edge.
 13. A mower blade, comprising: twosymmetrical body portions disposed on either side of an axis ofrotation; wherein each body portion includes a leading edge having afirst sharpened edge formed along at least a portion of the leadingedge, and a trailing edge having a second sharpened edge formed along atleast a portion of the trailing edge.
 14. The mower blade of claim 13,wherein each body portion tapers to a rounded end.
 15. The mower bladeof claim 14, wherein each body portion includes a lift feature.
 16. Themower blade of claim 13, wherein the leading edges are straight, andwherein the trailing edges are curved
 17. The mower blade of claim 16,wherein each body portion includes a lift feature.
 18. A mower bladecomprising: a mounting structure defining an axis of rotation aboutwhich the lawn mower blade is configured to rotate; a cutting portionextending in a first direction from the axis of rotation, wherein thecutting portion includes a lift feature and a leading edge having afirst sharpened edge formed along at least a portion of the leadingedge; and a counterweight portion extending in a second direction fromthe axis of rotation, the counterweight portion including acounterweight so that the center of mass of the mower blade lies on theaxis of rotation.
 19. The mower blade of claim 18, wherein the cuttingportion further includes a trailing edge opposite the leading edge andthe trailing edge includes a second sharpened edge formed along at leasta portion of the trailing edge.
 20. The mower blade of claim 19, whereinthe counterweight includes a sacrificial grinding portion and a leadingcounterweight edge having a third sharpened edge formed along at least aportion of the leading counterweight edge.